I'm probably foolish and slapdash, but who cares what grade-equivalent the colour filtration is? Just make a note and use the same next time you print the neg on that enlarger. If you use a different enlarger, then print up some standard negative on both systems and see how much to "aim off". Alternatively make two (differing) exposures - one each with max yellow and max magenta. If there is too much light for practical exposure manipulations, consider putting an old Cokin filter holder on the enlarger lens, with a neutral density filter in there.

The flimsy multicontrast filter sheets are intended for use in filter drawers and there is a more solid version made for under lens use. With these filters, the harder grades do seem harder than using magenta filtration, on my colour-head enlarger at least, but Grade-5 is rarely necessary.

You might find that a notional Grade-2 equivalent is a bit soft for an average neg, if you developed them for a condenser enlarger originally, but you can always bump up the magenta a bit.